1. Field of the Invention
The present invention relates to a running control system for performing a follow-running control in which a preceding vehicle is determined to be a target vehicle to be followed by the vehicle following.
2. Description of Related Art
Conventionally, in order to reduce the mental stress of a driver who needs to frequently repeat operations for advancing and stopping a vehicle on a congested road so as to follow the vehicle in front (i.e., the preceding vehicle), an automatic advancing and stopping system for vehicles is provided for determining the preceding vehicle to be followed by the present vehicle and thereby performing running control of the present vehicle so that the present vehicle automatically runs following advancing and stopping of the preceding vehicle.
More specifically, the running speed of the present vehicle is controlled in consideration of the relationship between the inter-vehicle distance with respect to the preceding vehicle detected by an inter-vehicle distance detection device and the necessary inter-vehicle distance determined by a safety inter-vehicle distance detecting device. That is, the running speed of the present vehicle is decreased when the relationship is in a deceleration region, while the running speed of the present vehicle is increased when the relationship is in an acceleration region. With the running control, mental stress of the driver can be reduced since the present vehicle automatically repeats advancing and stopping following the preceding vehicle (see, for example, Japanese Unexamined Patent Application, First Publication No. S60-19208).
In conventional systems, in order to eliminate a difference in driving sensation between running by the driver's manual operation and follow-running by the running control system, or in order to obtain consistency with operation by a cruise control system (i.e., an automatic constant speed running system), if the driver performs a braking operation, running control by the running control system is aborted and then the driving control is held by the driver. Therefore, in a case in which the brake is maintained ON by keeping the brake pedal depressed so as to stop the present vehicle, an operation for starting the running control is not accepted and the running control cannot be started.
More specifically, during running on a congested road in which rapid operations for acceleration and deceleration of the present vehicle are required, braking operations are often required in order to hold the running speed of the present vehicle low. Therefore, time of operation of the brake by the driver increases. In this case, chances to start control by the running control system are limited, thereby deteriorating operability of the present vehicle.